How does antibody participate in immune and inflammatory responses?
There are three main ways in which antibody is immunologically active:
1. Antibody can coat and neutralize invading organisms, not allowing the organism access to the host.
2. Two classes of antibody (IgM and IgG) activate (“fix”) complement by the classical pathway, resulting in cell chemotaxis, increased vascular permeability, and target cell lysis.
3. Antibody coats foreign particles, increasing the efficiency of phagocytosis by cells that contain surface Ig (Fc) receptors (neutrophils and macrophages). This process is called opsonization. Complement activation can also opsonize foreign particles facilitating removal through complement receptors.